To accelerate the kinetics of the oxygen reduction reaction (orr) in proton exchange membrane fuel cells, ultrafine pt nanoparticles modified with trace amounts of cobalt were fabricated and decorated on carbon black through a strategy involving modified glycol reduction and chemical etching. the obtained pt36co/c catalyst exhibits a much larger electrochemical surface area (ecsa) and an improved orr electrocatalytic activity compared to commercial pt/c. moreover, an electrode prepared with pt36co/c was further evaluated under h-2-air single cell test conditions, and exhibited a maximum specific power density of 10.27 w mg(pt)(-1),which is 1.61 times higher than that of a conventional pt/c electrode and also competitive with most state-of-the-art pt -based architectures. in addition, the changes in ecsa, power density, and reacting resistance during the accelerated degradation process further demonstrate the enhanced durability of the pt36co/c electrode. the superior performance observed in this work can be attributed to the synergy between the ultrasmall size and homogeneous distribution of catalyst nanoparticles, bimetallic ligand and electronic effects, and the dissolution of unstable co with the rearrangement of surface structure brought about by acid etching. furthermore, the accessible raw materials and simplified operating procedures involved in the fabrication process would result in great cost-effectiveness for practical applications of pemfcs. (c) 2019, dalian institute of chemical physics, chinese academy of sciences. published by elsevier b.v. all rights reserved.